Bag for street photography, city sightseeing

during my travels abroad I'm used to carry my gear with a Lowepro backpack (Computrekker AW); there is enough space for gear, tablet and some other and on the airplane I can have as hand luggage near me.

But when I arrive in a place and visit some cities or walk around in the country, I would like to have some "lighter" and less cumbersome (or rather, leave the backpack in hotel and go around with a shoulder/sling/belt/somewhat else)

My travel kit is essentially a 5D II with 24-105L attached, plus a 70-200f4L and a 12-24 sigma.

I was considering something like Think Tank Retrospective 10 (or maybe the 7 is enough ?), but before the purchase I kindly ask you some help and advices on what you prefer as bag type and other models you chose.